The present invention relates generally to a method and means for making stairs The invented method allows rapid, efficient, accurate, and economical construction of stairs, either straight or curved, whether a single step or an entire flight of steps. The invented method is surprisingly adaptable to a variety of stairways and produces steps that are incredibly quiet and squeak free. Furthermore, the invented method allows the production of a flight of steps of unlimited length and a surprisingly sturdy means of support.
Conventional stairs for residential construction include a stringer made from a 2×12 piece of wood, with triangular portions of the stringer cut away to define the rise and run of each step. This construction requires that each triangle of removed material be marked and cut separately, involving much labor and presenting numerous opportunities for error and injury. It also results in a stringer having an effective structural thickness of only about half the thickness of the original 2×12 piece of lumber with approximately one-quarter of the original 2×12 piece being thrown away and therefore wasted.
The conventional method of stair construction has additional problems. The moisture content of the good is an inherent variable in that, as the wood dries, it shrinks in size allowing nail's or screws to loosen in time and cause squeaks. It also produces an “out-of-square” condition as the flood shrinks in width at a rate more pronounced than it does in length. This creates a need to relevel the tread and risers with the use of shims so that the finished tread and riser surfaces will be square to each other.
There is also a common problem in the use of the conventional method for exterior use where there is more exposure to the elements. Wood that repeatedly gets wet and dries out will split, again loosening nails or screws. The triangular portion holding the tread and riser inevitably breaks off.
Another inherent problem with the conventional method is with the use of dimensional lumber and finding a good, straight board, without knots in longer lengths.
Other attempts at solving the problems of conventional construction techniques for stairs take a modularized approach. Two examples of modularized stairs are shown in U.S. Pat. Nos. 1,925,642 and 4,875,315, the disclosures of which are incorporated herein by reference. In these patents, a composite stringer is made from triangular-shaped blocks attached to a stringer of approximately 2×6-inches in size, using a tongue-and-groove connection. In each of these disclosures, the stringer must be cut separately if the rise or run of the stairs varies from a predetermined rise and run.
Other prior art, including U.S. Pat. Nos. 2,724,466; 4,015,687; 4,106,591; 4,635,416; 4,709,520; 4,866,894; and 5,205,093, the disclosures of which are incorporated herein, disclose various brackets for use with unaltered structural lumber or steel. However, several of these have a pre-defined rise and run for each step or to the extent that some adjustability is allowed are labor-intensive and unwieldy in application.
New construction techniques such as those applied in construction of metal framed homes require, due to fire codes, that the stairs be constructed of steel. Attempts at solving this problem include my previous U.S. Pat. No. 6,088,977, as well as U.S. Pat. No. 5,791,101 (Wallace) where the use of a bracket or a component was implied to secure the tread and riser. This helps, however it requires the addition of shim material to create a smooth surface to apply the finish materials to the outside surface of the finished stringer. There is assembly time and use of fasteners or other components. The present invention solves all of the above identified problems.
It is the object of the present invention to provide a device and method that is economical to manufacture and that may be used to make stairs accurately efficiently, and securely.
It is a further object of the present invention to provide a method of making curved stairs with a tight radius.
It is a further object of the present invention to provide a method of making stairs straight or curved.
It is a further object of the present invention to provide a method that reduces the amount of lumber that is wasted in the manufacturing of stairs.
Additional objects and advantages of the present invention will be understood more readily after a consideration of the drawings and the Detailed Description of the Preferred Embodiment.
The embodiment can be fabricated from one contiguous piece of sheet metal or several smaller pieces joined together by means of welding, fasteners, etc. A desired rise and run are then cut out with the allowance for extra material to provide for the tread and riser support flanges.
The flanges are then formed inward to create a surface for attaching treads and risers. A flange is formed on the bottom edge of the stringer to create a surface whereby structural or finished material can be applied, as well as increase rigidity in the embodiment.
Flanges are provided for mounting or attaching to a structure.
The contiguous surface of the invention yielded surprising results. It provided a load carrying support for the tread surfaces that resisted bouncing when loads were applied. The application of a bottom flange added more rigidity.
It is also believed that the tread support flanges cooperates with most conventional fasteners to provide an attachment that is secure and very resistant to squeaking or making other noises as weight is transferred onto and off the step. For optimum results, screws or fasteners that attach by means of threads should be used.
The use of sheet metal eliminates all the inherent disadvantages found in dimensional lumber, such as the cracking caused by moisture fluctuations as well as the loosening of fasteners and shrinkage incurred in wood. It also provides safety due to it being fire resistant.
Another advantage is the consistency and uniformity found in metals. It makes for accurate calculations for determining load capacity.
There is very little waste as the pieces can be nested on a standard size sheet of metal, then cut out through the implementation of laser, waterjet, plasma, or stamping dies. All scrap produced can be recycled through conventional means. With properly plated or with proper coatings applied, the invention will weather outside fully exposed to the elements without failure.
Since there are no attached pieces as in the modular method of stair construction there are fewer fasteners that can fail and no need to shim surfaces to create a smooth outer surface on which to apply finishes such as veneers or paint.
With the addition of slits to the tread support flange, the preferred embodiment can be flexed or curved to create a wide variety of configurations. The addition of laminated materials to the surface of the invention increases strength by preventing the sheet metal from distorting, as well as providing a surface to attach finished or structural materials.
On multiple-stringer stair systems the flanges can be formed away from the outside finished surface so that they conveniently stack one into the other, reducing shelf space as well as shipping space and thereby reducing freight costs.